What is $\int_0^{\frac{\pi}{2}} \frac{d x}{a^2 \cos ^2 x+b^2 \sin ^2 x}$ equal to?

• A

  $2 a b$
• B

  $2 \pi a b$
• Correct answer
  C

  $\frac{\pi}{2 a b}$
• D

  $\frac{\pi}{a b}$

Hence, the correct answer is option: 'C'.